Simulations On The Structural Regulation And Performance Of MO₂(M=Mo?W) Nanosheets As Anode For Lithium-ion Batteries

The rapid development of lithium-ion battery related industries makes it difficult for traditional anode material graphite to meet its higher performance requirements.Transition metal compounds have become potential cathode materials for high efficiency lithium-ion batteries because of their large comparative area,chemical stability and low cost.In this paper,the crystal structure,electronic properties,Li adsorption and diffusion properties of MO₂(M=Mo,W)nanosheets used as anode materials for lithium-ion batteries were studied by first principles calculation method.First,according to the existing two-dimensional transition metal compound MX₂(M=Mo,W;X=O,S),the MO₂/MS₂ heterojunction was constructed,and the electronic properties,adsorption and diffusion of Li in the interlayer of heterojunctions were calculated.Due to the strain and van der Waals force when forming the heterojunction,the band gap of the heterojunction is extremely small.Li can be spontaneously adsorbed between the layers of the heterojunction without cluster,and the diffusion barrier is similar to the single-layer two-dimensional transition metal compound,showing good rate performance.The construction of heterojunctions can effectively improve the performance of transition metal compounds as anode materials for lithium-ion batteries.Then,a new type of two-dimensional porous WO₂ structure was designed and the stability of this structure was determined by Mo doping modification,and the electronic properties and Li adsorption and diffusion properties were calculated and studied.The new two-dimensional porous Mo_0.5W_0.5O₂ structure itself has a narrow band gap.Although it is a semiconductor,it has a certain conductive basis.After Li is adsorbed,the structure becomes metallic,the conductivity is greatly improved,and the diffusion barrier of Li on the surface of the structure is relatively small.This new type of of two-dimensional porous material is a potential anode material for lithium-ion batteries.Finally,two-dimensional porous MO₂(M=Mo,W)structures with different thicknesses were designed by adjusting the thickness,and the electronic properties and Li adsorption and diffusion properties of these structures were calculated.The calculation results of electronic properties show that these structures themselves have metallic properties,and the electrical conductivity is guaranteed.The study of Li adsorption found that only five-layer two-dimensional porous WO₂structure has more regular adsorption,and the diffusion barrier is the smallest among the WO₂materials currently studied.The 5-layer two-dimensional porous WO₂ structure is a promising anode material for lithium-ion batteries.